Method and apparatus for transfer of semiconductor devices

ABSTRACT

A system to transfer an unpackaged die directly from a die holding substrate to a transfer location on a secondary substrate. The system includes a die separation device disposed adjacent to the die holding substrate to initiate separation of the unpackaged die from the die holding substrate. An energy source is disposed adjacent to the secondary substrate to apply energy to the transfer location and affix the unpackaged die directly to the secondary substrate. A sensor detects a position and orientation of the secondary substrate with respect to the unpackaged die on the die holding substrate. A processor is in communication with the die separation device, the energy source, and the sensor. The processor is configured to cause actuation of the die separation device and the energy source according, at least in part, to transfer instructions and data received from the sensor.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 15/074,994, filed on Mar. 18, 2016, entitled“Method for Transfer of Semiconductor Devices,” which is now patented asU.S. Pat. No. 9,871,023 and which is a continuation of and claimspriority to U.S. patent application Ser. No. 14/939,896, filed on Nov.12, 2015, entitled “Apparatus for Transfer of Semiconductor Devices,”which is now patented as U.S. Pat. No. 9,633,883, and which claimspriority to U.S. Provisional Patent Application No. 62/146,956, filed onApr. 13, 2015, and to U.S. Provisional Patent Application No.62/136,434, filed on Mar. 20, 2015, which applications are herebyincorporated in their entirety by reference.

BACKGROUND

Semiconductor devices are electrical components that utilizesemiconductor material, such as silicon, germanium, gallium arsenide,and the like. Semiconductor devices are typically manufactured as singlediscrete devices or as integrated circuits (ICs). Examples of singlediscrete devices include electrically-actuatable elements such aslight-emitting diodes (LEDs), diodes, transistors, resistors,capacitors, fuses, and the like.

The fabrication of semiconductor devices typically involves an intricatemanufacturing process with a myriad of steps. The end-product of thefabrication is a “packaged” semiconductor device. The “packaged”modifier refers to the enclosure and protective features built into thefinal product as well as the interface that enables the device in thepackage to be incorporated into an ultimate circuit.

The conventional fabrication process for semiconductor devices startswith handling a semiconductor wafer. The wafer is diced into a multitudeof “unpackaged” semiconductor devices. The “unpackaged” modifier refersto an unenclosed semiconductor device without protective features.Herein, unpackaged semiconductor devices may be called semiconductordevice dies, or just “dies” for simplicity. A single semiconductor wafermay be diced to create dies of various sizes, so as to form upwards ofmore than 100,000 or even 1,000,000 dies from the semiconductor wafer(depending on the starting size of the semiconductor), and each die hasa certain quality. The unpackaged dies are then “packaged” via aconventional fabrication process discussed briefly below. The actionsbetween the wafer handling and the packaging may be referred to as “diepreparation.”

In some instances, the die preparation may include sorting the dies viaa “pick and place process,” whereby diced dies are picked upindividually and sorted into bins. The sorting may be based on theforward voltage capacity of the die, the average power of the die,and/or the wavelength of the die.

Typically, the packaging involves mounting a die into a plastic orceramic package (e.g., mold or enclosure). The packaging also includesconnecting the die contacts to pins/wires forinterfacing/interconnecting with ultimate circuitry. The packaging ofthe semiconductor device is typically completed by sealing the die toprotect it from the environment (e.g., dust).

A product manufacturer then places packaged semiconductor devices inproduct circuitry. Due to the packaging, the devices are ready to be“plugged in” to the circuit assembly of the product being manufactured.Additionally, while the packaging of the devices protects them fromelements that might degrade or destroy the devices, the packaged devicesare inherently larger (e.g., in some cases, around 10 times thethickness and 10 times the area, resulting in 100 times the volume) thanthe die found inside the package. Thus, the resulting circuit assemblycannot be any thinner than the packaging of the semiconductor devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The Detailed Description is set forth with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different figures indicates similaror identical items. Furthermore, the drawings may be considered asproviding an approximate depiction of the relative sizes of theindividual components within individual figures. However, the drawingsare not to scale, and the relative sizes of the individual components,both within individual figures and between the different figures, mayvary from what is depicted. In particular, some of the figures maydepict components as a certain size or shape, while other figures maydepict the same components on a larger scale or differently shaped forthe sake of clarity.

FIG. 1 illustrates an isometric view of an embodiment of a transferapparatus.

FIG. 2A represents a schematic view of an embodiment of a transferapparatus in a pre-transfer position.

FIG. 2B represents a schematic view of an embodiment of a transferapparatus in a transfer position.

FIG. 3 illustrates an embodiment of a shape profile of the end of aneedle of a transfer mechanism.

FIG. 4 illustrates an embodiment of a needle actuation stroke profile.

FIG. 5 illustrates a plan view of an embodiment of a product substratehaving a circuit trace thereon.

FIG. 6 illustrates a schematic view of an embodiment of elements of adie transfer system.

FIG. 7 illustrates a schematic view of an embodiment of a circuitry pathbetween machine hardware and controllers of a die transfer system.

FIG. 8 illustrates a method of a die transfer process according to anembodiment of this application.

FIG. 9 illustrates a method of a die transfer operation according to anembodiment of this application.

FIG. 10 illustrates an embodiment of a direct transfer apparatus andprocess implementing a conveyor system.

FIG. 11A illustrates a schematic view of another embodiment of atransfer apparatus in a pre-transfer position.

FIG. 11B illustrates a schematic top view of the product substrateconveyance mechanism post-transfer operation of the embodiment in FIG.11A.

FIG. 12 illustrates a schematic view of another embodiment of a transferapparatus in a pre-transfer position.

FIG. 13 illustrates a schematic view of another embodiment of a transferapparatus in a pre-transfer position.

DETAILED DESCRIPTION

This disclosure is directed to a machine that directly transfers andaffixes semiconductor device dies to a circuit and to the process forachieving the same, as well as to the circuit having dies affixedthereto (as the output product). In some instances, the machinefunctions to transfer unpackaged dies directly from a substrate such asa “wafer tape” to a product substrate, such as a circuit substrate. Thedirect transfer of unpackaged dies may significantly reduce thethickness of an end product compared to a similar product produced byconventional means, as well as the amount of time and/or cost tomanufacture the product substrate.

For the purpose of this description, the term “substrate” refers to anysubstance on which, or to which, a process or action occurs. Further,the term “product” refers to the desired output from a process oraction, regardless of the state of completion. Thus, a product substraterefers to any substance on which, or to which, a process or action iscaused to occur for a desired output.

In an embodiment, the machine may secure a product substrate forreceiving “unpackaged” dies, such as LEDs, transferred from the wafertape, for example. In an effort to reduce the dimensions of the productsusing the dies, the dies are very small and thin, for example, a die maybe about 50 microns thick. Due to the relatively small size of the dies,the machine includes components that function to precisely align boththe wafer tape carrying the dies and the product substrate to ensureaccurate placement and/or avoid product material waste. In someinstances, the components that align the product substrate and the dieson the wafer tape may include a set of frames in which the wafer tapeand the product substrate are secured respectively and conveyedindividually to a position of alignment such that a specific die on thewafer tape is transferred to a specific spot on the product substrate.

The frame that conveys the product substrate may travel in variousdirections, including horizontal directions and/or vertical directions,or even directions that would permit transfer to a curved surface. Theframe that conveys the wafer tape may travel in various directions also.A system of gears, tracks, motors, and/or other elements may be used tosecure and convey the frames carrying the product substrate and thewafer tape respectively to align the product substrate with the wafertape in order to place a die on the correct position of the productsubstrate. Each frame system may also be moved to an extraction positionin order to facilitate extraction of the wafer tape and the productsubstrate upon completion of the transfer process.

In some instances, the machine may further include a transfer mechanismfor transferring the dies directly from the wafer tape to the productsubstrate without “packaging” the dies. The transfer mechanism may bedisposed vertically above the wafer tape so as to press down on the diesvia the wafer tape toward the product substrate. This process ofpressing down on the dies may cause the dies to peel off of the wafertape, starting at the sides of the dies until the dies separate from thewafer tape to be attached to the product substrate. That is, by reducingthe adhesion force between the die and the wafer tape, and increasingthe adhesion force between the die and the product substrate, the diemay be transferred.

In some embodiments, the transfer mechanism may include an elongatedrod, such as a pin or needle that may be cyclically actuated against thewafer tape to push the wafer tape from a top side. The needle may besized so as to be no wider than a width of the die being transferred.Although in other instances, the width of the needle may wider, or anyother dimension. When the end of the needle contacts the wafer tape, thewafer tape may experience a local deflection at the area between the dieand the wafer tape. Inasmuch as the deflection is highly localized andrapidly performed, the portion of the wafer tape that does not receivepressure from the needle may begin to flex away from the surface of thedie. This partial separation may thus cause the die to lose sufficientcontact with the wafer tape, so as to be released from the wafer tape.Moreover, in some instances, the deflection of the wafer tape may be sominimal, as to maintain an entirety of the surface area of the die incontact with the wafer tape, while still causing the opposing surface ofthe die to extend beyond a plane of extension of the correspondingsurface of the adjacent dies to avoid unintentional transfer of theadjacent dies.

Alternatively, or additionally, the machine may further include a fixingmechanism for affixing the separated, “unpackaged” dies to the productsubstrate. In some instances, the product substrate may have thereon acircuit trace to which the dies are transferred and affixed. The fixingmechanism may include a device that emits energy, such as a laser, tomelt/soften the material of the circuit trace on the product substrate.Moreover, in some instances, the laser may be used to activate/hardenthe material of the circuit trace. Thus, the fixing mechanism may beactuated before, and/or after the die is in contact with the material ofthe circuit trace. Accordingly, upon actuation of the transfer mechanismto release a die onto the product substrate, the energy emitting devicemay also be activated so as to prepare the trace material to receive thedie. The activation of the energy emitting device may further enhancethe release and capture of the die from the wafer tape so as to beginformation of a semiconductor product on the product substrate.

First Example Embodiment of a Direct Transfer Apparatus

FIG. 1 illustrates an embodiment of an apparatus 100 that may be used todirectly transfer unpackaged semiconductor components (or “dies”) from awafer tape to a product substrate. The wafer tape may also be referredto herein as the semiconductor device die substrate, or simply a diesubstrate. The apparatus 100 may include a product substrate conveyancemechanism 102 and a wafer tape conveyance mechanism 104. Each of theproduct substrate conveyance mechanism 102 and the wafer tape conveyancemechanism 104 may include a frame system or other means to secure therespective substrates to be conveyed to desired alignment positions withrespect to each other. The apparatus 100 may further include a transfermechanism 106, which, as shown, may be disposed vertically above thewafer tape conveyance mechanism 104. In some instances, the transfermechanism 106 may be located so as to nearly contact the wafersubstrate. Additionally, the apparatus 100 may include a fixingmechanism 108. The fixing mechanism 108 may be disposed verticallybeneath the product substrate conveyance mechanism 102 in alignment withthe transfer mechanism 106 at a transfer position, where a die may beplaced on the product substrate. As discussed below, FIGS. 2A and 2Billustrate example details of the apparatus 100.

Inasmuch as FIGS. 2A and 2B depict different stages of the transferoperation, while referring to the same elements and features ofapparatus 200, the following discussion of specific features may referinterchangeably to either or both of FIGS. 2A and 2B, except whereexplicitly indicated. In particular, FIGS. 2A and 2B illustrate anembodiment of an apparatus 200, including a product substrate conveyancemechanism 202, a wafer tape conveyance mechanism 204, a transfermechanism 206, and a fixing mechanism 208. The product substrateconveyance mechanism 202 may be disposed adjacent to the wafer tapeconveyance mechanism 204. For example, as illustrated, the productsubstrate conveyance mechanism 202 may extend in a substantiallyhorizontal direction and may be disposed vertically beneath the wafertape conveyance mechanism 204 so as to take advantage of any effect thatgravity may have in the transfer process. Alternatively, the productsubstrate conveyance mechanism 202 may be oriented so as to extendtransversely to a horizontal plane.

During a transfer operation, the conveyance mechanisms 202, 204 may bepositioned such that a space between a surface of a product substratecarried by the product substrate conveyance mechanism 202 and a surfaceof a wafer tape carried by the wafer tape conveyance mechanism 204 maybe more or less than 1 mm, depending on various other aspects of theapparatus 200, including the amount of deflection that occurs bycomponents during the transfer operation, as described herein below. Insome instances, the respective opposing surfaces of the wafer tape andthe product substrate may be the most prominent structures in comparisonto the supporting structures of the conveyance mechanisms 202, 204. Thatis, in order to avoid a collision between components of the machine andproducts thereon, which might be caused by movable parts (e.g., theconveyance mechanisms 202, 204), a distance between the respectivesurfaces of the wafer tape and product substrate may be less than adistance between either of the surfaces and any other opposingstructural component.

As depicted, and in some instances, the transfer mechanism 206 may bedisposed vertically above the wafer tape conveyance mechanism 204, andthe fixing mechanism 208 may be disposed vertically beneath the productsubstrate conveyance mechanism 202. It is contemplated that in someembodiments, one or both of the transfer mechanism 206 and the fixingmechanism 208 may be oriented in different positions than the positionsillustrated in FIGS. 2A and 2B. For example, the transfer mechanism 206may be disposed so as to extend at an acute angle with respect to ahorizontal plane. In another embodiment, the fixing mechanism 208 may beoriented to emit energy during the transfer process from the samedirection of actuation as the transfer mechanism 206, or alternatively,from any orientation and position from which the fixing mechanism 208 isable to participate in the transfer process.

The product substrate conveyance mechanism 202 may be used to secure aproduct substrate 210. Herein, the term “product substrate” may include,but is not limited to: a wafer tape (for example, to presort the diesand create sorted die sheets for future use); a paper or polymersubstrate formed as a sheet or other non-planar shape, where thepolymer—translucent or otherwise—may be selected from any suitablepolymers, including, but not limited to, a silicone, an acrylic, apolyester, a polycarbonate, etc.; a circuit board (such as a printedcircuit board (PCB)); a string or thread circuit, which may include apair of conductive wires or “threads” extending in parallel; and a clothmaterial of cotton, nylon, rayon, leather, etc. The choice of materialof the product substrate may include durable materials, flexiblematerials, rigid materials, and other materials with which the transferprocess is successful and which maintain suitability for the end use ofthe product substrate. The product substrate 210 may be formed solely orat least partially of conductive material such that the productsubstrate 210 acts as a conductive circuit for forming a product. Thepotential types of product substrate may further include items, such asglass bottles, vehicle windows, or sheets of glass.

In an embodiment as depicted in FIGS. 2A and 2B, the product substrate210 may include a circuit trace 212 disposed thereon. The circuit trace212, as depicted, may include a pair of adjacent trace lines spacedapart by a trace spacing, or gap so as to accommodate a distance betweenelectrical contact terminals (not shown) on the dies being transferred.Thus, the trace spacing, or gap between the adjacent trace lines of thecircuit trace 212 may be sized according to the size of the die beingtransferred to ensure proper connectivity and subsequent activation ofthe die. For example, the circuit trace 212 may have a trace spacing, orgap ranging from about 75 to 200 microns, about 100 to 175 microns, orabout 125 to 150 microns.

The circuit trace 212 may be formed from a conductive ink disposed viascreen printing, inkjet printing, laser printing, manual printing, orother printing means. Further, the circuit trace 212 may be pre-curedand semi-dry or dry to provide additional stability, while still beingactivatable for die conductivity purposes. A wet conductive ink may alsobe used to form the circuit trace 212, or a combination of wet and dryink may be used for the circuit trace 212. Alternatively, oradditionally, the circuit trace 212 may be pre-formed as a wire trace,or photo-etched, or from molten material formed into a circuit patternand subsequently adhered, embedded, or otherwise secured to the productsubstrate 210.

The material of the circuit trace 212 may include, but is not limitedto, silver, copper, gold, carbon, conductive polymers, etc. In someinstances, the circuit trace 212 may include a silver-coated copperparticle. A thickness of the circuit trace 212 may vary depending on thetype of material used, the intended function and appropriate strength orflexibility to achieve that function, the energy capacity, the size ofthe LED, etc. For example, a thickness of the circuit trace may rangefrom about 5 microns to 20 microns, from about 7 microns to 15 microns,or from about 10 microns to 12 microns.

Accordingly, in one non-limiting example, the product substrate 210 maybe a flexible, translucent polyester sheet having a desired circuitpattern screen printed thereon using a silver-based conductive inkmaterial to form the circuit trace 212.

The product substrate conveyance mechanism 202 may include a productsubstrate conveyor frame 214 for securing a product substrate holderframe 216. The structure of the product substrate holder frame 216 mayvary significantly depending on the type and properties (e.g., shape,size, elasticity, etc.) of the product substrate being used. Inasmuch asthe product substrate 210 may be a flexible material, product substrate210 may be held under tension in the product substrate holder frame 216,so as to create a more rigid surface upon which a transfer operation,discussed herein below, is performed. In the above example, the rigiditycreated by the tension in the product substrate 210 may increase theplacement accuracy when transferring components.

In some instances, using a durable or more rigid material for theproduct substrate 210, naturally provides a firm surface for componentplacement accuracy. In contrast, when the product substrate 210 isallowed to sag, wrinkles and/or other discontinuities may form in theproduct substrate 210 and interfere with the pre-set pattern of thecircuit trace 212, to the extent that the transfer operation may beunsuccessful.

While the means of holding the product substrate 210 may vary greatly,FIG. 2A illustrates an embodiment of a product substrate holder frame216 including a first portion 216 a having a concave shape and a secondportion 216 b having a convex counter shape that corresponds in shape tothe concave shape. In the depicted example, tension is created for theproduct substrate 210 by inserting an outer perimeter of the productsubstrate 210 between the first portion 216 a and the second portion 216b to thereby clamp the product substrate 210 tightly.

The product substrate conveyor frame 214 may be conveyed in at leastthree directions—two directions in the horizontal plane and verticallyas well. The conveyance may be accomplished via a system of motors,rails, and gears (none of which are shown). As such, the productsubstrate tensioner frame 216 may be conveyed to and held in a specificposition as directed and/or programmed and controlled by a user of theapparatus 200.

The wafer tape conveyance mechanism 204 may be implemented to secure awafer tape 218 having dies 220 (i.e., semiconductor device dies)thereon. The wafer tape 218 may be conveyed in multiple directions tothe specific transfer positions for the transfer operation via a wafertape conveyor frame 222. Similar to the product substrate conveyor frame214, the wafer tape conveyor frame 222 may include a system of motors,rails, and gears (none of which are shown).

The unpackaged semiconductor dies 220 for transfer may be extremelysmall. Indeed, the height of the dies 220 may range from 12.5 to 200microns, or from 25 to 100 microns, or from 50 to 80 microns.

Due to the micro size of the dies, when the wafer tape 218 has beenconveyed to the appropriate transfer position, a gap spacing between thewafer tape 218 and the product substrate 210 may range from about 0.25mm to 1.50 mm, or about 0.50 mm to 1.25 mm, or about 0.75 mm to 1.00 mm,for example. A minimum gap spacing may depend on factors including: athickness of the die being transferred, a stiffness of the wafer tapeinvolved, an amount of deflection of the wafer tape needed to provideadequate capture and release of the die, a proximity of the adjacentdies, etc. As the distance between the wafer tape 218 and the productsubstrate 210 decreases, a speed of the transfer operation may alsodecrease due to the reduced cycle time (discussed further herein) of thetransfer operation. Such a decrease in the duration of a transferoperation may therefore increase a rate of die transfers. For example,the die transfer rate may range from about 6-20 dies placed per second.

Furthermore, the wafer tape conveyor frame 222 may secure a wafer tapeholder frame 224, which may stretch and hold the wafer tape 218 undertension. As illustrated in FIG. 2A, the wafer tape 218 may be secured inthe wafer tape holder frame 224 via clamping a perimeter of the wafertape 218 between adjacent components of the wafer holder frame 224. Suchclamping assists in maintaining the tension and stretched characteristicof the wafer tape 218, thereby increasing the success rate of thetransfer operation. In view of the varying properties of differenttypes/brands/qualities of wafer tapes available, a particular wafer tapemay be selected for use based on an ability to consistently remain at adesired tension during a transfer process. In some instances, the needleactuation performance profile (discussed further herein below) maychange depending on the tension of the wafer tape 218.

The material used for the wafer tape 218 may include a material havingelastic properties, such as a rubber or silicone, for example.Furthermore, inasmuch as temperature of the environment and the wafertape 218 itself may contribute to potential damage to the wafer tape 218during the transfer process, a material having properties that areresistant to temperature fluctuation may be advantageous. Additionally,in some instances, the wafer tape 218 may be stretched slightly so as tocreate a separation or gap between individual dies 220 to assist in thetransfer operation. A surface of the wafer tape 218 may include a stickysubstance via which the dies 220 may be removably adhered to the wafertape 218.

The dies 220 on the wafer tape 218 may include dies that wereindividually cut from a solid semiconductor wafer and then placed ontothe wafer tape 218 to secure the dies. In such a situation, the dies mayhave been pre-sorted and explicitly organized on the wafer tape 218, inorder, for example, to assist in the transfer operation. In particular,the dies 220 may be arranged sequentially as to the expected order oftransfer to the product substrate 210. Such pre-arrangement of the dies220 on the wafer tape 218 may reduce the amount of travel that wouldotherwise occur between the product substrate conveyance mechanism 202and the wafer tape conveyance mechanism 204. Additionally, oralternatively, the dies on the wafer tape 218 may have been pre-sortedto include only dies having substantially equivalent performanceproperties. In this case, efficiency of the supply chain may beincreased and thus, travel time of the wafer tape conveyance mechanism204 may be reduced to a minimum.

In some instances, materials used for the dies may include, but is notlimited to, silicon carbide, gallium nitride, a coated silicon oxide,etc. Furthermore, sapphire or silicon may be used as a die as well.Additionally, as indicated above, a “die” may be representative hereinof an electrically actuatable element generally.

In some embodiments, the wafer tape 218 may include dies that are notpre-sorted, but rather are formed by simply cutting a semiconductordirectly on wafer tape, and then leaving the dies on the wafer tapewithout “picking and placing” to sort the dies depending on therespective performance quality of the dies. In such a situation, thedies on the wafer tape may be mapped to describe the exact relativelocations of the different quality dies. Therefore, in some instances,it may be unnecessary to use wafer tape having pre-sorted dies. In sucha case, the amount of time and travel for the wafer tape conveyancemechanism 204 to move between particular dies for each sequentialtransfer operation may increase. This may be caused in part by thevarying quality of the dies dispersed within the area of thesemiconductor, which means that a die of a specific quality for the nexttransfer operation may not be immediately adjacent to the previouslytransferred die. Thus, the wafer tape conveyance mechanism 204 may movethe wafer tape 218 further to align an appropriate die of a specificquality for transfer than would be necessary for a wafer tape 218containing dies of substantially equivalent quality.

In further regard to the dies 220 on the wafer tape 218, in someinstances, a data map of the dies 220 may be provided with the wafertape 218. The data map may include a digital file providing informationthat describes the specific quality and location of each die on thewafer tape 218. The data map file may be input into a processing systemin communication with the apparatus 200, whereby the apparatus 200 maybe controlled/programmed to seek the correct die 220 on the wafer tape218 for transfer to the product substrate 210.

A transfer operation is performed, in part, via the transfer mechanism206, which is a die separation device for assisting in separation ofdies from the wafer tape 218. The actuation of the transfer mechanism206 may cause one or more dies 220 to be released from the wafer tape218 and to be captured by the product substrate 210. In some instances,the transfer mechanism 206 may operate by pressing an elongated rod,such as a pin or a needle 226 into a top surface of the wafer tape 218against a die 220. The needle 226 may be connected to a needle actuator228. The needle actuator 228 may include a motor connected to the needle226 to drive the needle 226 toward the wafer tape 218 atpredetermined/programmed times.

In view of the function of the needle 226, the needle 226 may include amaterial that is sufficiently durable to withstand repetitive, rapid,minor impacts while minimizing potential harm to the dies 220 uponimpact. For example, the needle 226 may include a metal, a ceramic, aplastic, etc. Additionally, a tip of the needle 226 may have aparticular shape profile, which may affect the ability of the needle tofunction repetitively without frequently breaking either the tip ordamaging the wafer tape 218 or the dies 220. The profile shape of thetip of the needle is discussed in greater detail below with respect toFIG. 3.

In a transfer operation, the needle 226 may be aligned with a die 220,as depicted in FIG. 2A, and the needle actuator may move the needle 226to push against an adjacent side of the wafer tape 218 at a position inwhich the die 220 is aligned on the opposing side of the wafer tape 218,as depicted in FIG. 2B. The pressure from the needle 226 may cause thewafer tape 218 to deflect so as to extend the die 220 to a positioncloser to the product substrate 226 than adjacent dies 220, which arenot being transferred. As indicated above, the amount of deflection mayvary depending several factors, such as the thickness of the die andcircuit trace. For example, where a die 220 is about 50 microns thickand circuit trace 212 is about 10 microns thick, an amount of deflectionof the wafer tape 218 may be about 75 microns. Thus, the die 220 may bepressed via the needle 226 toward the product substrate 210 to theextent that the electrical contact terminals (not shown) of the die areable to bond with the circuit trace 212, at which point, the transferoperation proceeds to completion and the die 220 is released from thewafer tape 218.

To the extent that the transfer process may include a rapidly repeatedset of steps including a cyclical actuation of the needle 226 pressingupon a die 220, a method of the process is described in detail hereinbelow with respect to FIG. 8. Further, the stroke profile of theactuation of the needle 226 (within the context of the transfer process)is discussed in more detail hereafter with respect to FIG. 4.

Turning back to FIGS. 2A and 2B, in some instances, the transfermechanism 206 may further include a needle retraction support 230, (alsoknown as a pepper pot). In an embodiment, the support 230 may include astructure having a hollowed space wherein the needle 226 may beaccommodated by passing into the space via an opening 232 in a first endof the support 230. The support 230 may further include at least oneopening 234 on a second opposing end of the support 230. Moreover, thesupport may include multiple perforations near opening 234. The at leastone opening 234 may be sized with respect to a diameter of the needle226 to accommodate passage of the needle 226 therethrough so as to presson the wafer tape 218 during the transfer process.

Additionally, in some instances, the support 230 may be disposedadjacent to the upper surface of the wafer tape 218. As such, when theneedle 226 is retracted from pressing on the wafer tape 218 during atransfer operation, a base surface of the support 230 (having the atleast one opening 234 therein) may come into contact with the uppersurface of the wafer tape 218, thereby preventing upward deflection ofthe wafer tape 218. This upward deflection may be caused in the eventwhere the needle 226 pierces at least partially into the wafer tape 218,and while retracting, the wafer tape is stuck to the tip of the needle226. Thus, the support 230 may reduce the time it takes to move to thenext die 220. A wall perimeter shape of the support 230 may becylindrical or any other shape that may be accommodated in the apparatus200. Accordingly, the support 230 may be disposed between the needle 226and an upper surface of the wafer tape 218.

With respect to the effect of temperature on the integrity of the wafertape 218, it is contemplated that a temperature of support 230 may beadjusted so as to regulate the temperature of the needle 226 and thewafer tape 218, at least near the point of the transfer operation.Accordingly, the temperature of the support 230 may be heated or cooled,and a material of the support 230 may be selected to maximize thermalconductivity. For example, the support 230 may be formed of aluminum, oranother relatively high thermal conductivity metal or comparablematerial, whereby the temperature may be regulated to maintainconsistent results of the transfer operations. In some instances, airmay be circulated within the support 230 to assist in regulating thetemperature of a local portion of the wafer tape 218. Additionally, oralternatively, a fiber optic cable 230 a may be inserted into the needleretraction support 230, and may further be against the needle 226 toassist in temperature regulation of the wafer tape 218 and/or the needle226.

As indicated above, fixing mechanism 208 may assist in affixing the die220 to the circuit trace 212 on a surface of the product substrate 210.FIG. 2B illustrates the apparatus 200 in a transfer stage, where the die220 is pushed against the circuit trace 212. In an embodiment, fixingmechanism 208 may include an energy-emitting device 236 including, butnot limited to, a laser, electromagnetic radiation, pressure vibration,ultrasonic welding, etc. In some instances, the use of pressurevibration for the energy-emitting device 236 may function by emitting avibratory energy force so as to cause disruption of the molecules withinthe circuit trace against those of the electrical contact terminals soas to form a bond via the vibratory pressure.

In a non-limiting example, as depicted in FIG. 2B, a laser may beimplemented as the energy-emitting device 236. During a transferoperation, laser 236 may be activated to emit a specific wavelength andintensity of light energy directed at the die 220 being transferred. Thewavelength of the light of the laser 236 may be selected specificallybased on the absorption of that wavelength of light with respect to thematerial of the circuit trace 212 without significantly affecting thematerial of the product substrate 210. For example, a laser having anoperational wavelength of 808 nm, and operating at 5 W may be readilyabsorbed by silver, but not by polyester. As such, the laser beam maypass through the substrate of polyester and affect the silver of acircuit trace. Alternatively, the wavelength of laser may match theabsorption of the circuit trace and the material of the substrate. Thefocus area of the laser 236 (indicated by the dashed lines emanatingvertically from the laser 236 in FIG. 2B toward the product substrate210) may be sized according to the size of the LED, such as for example,a 300 micron wide area.

Upon actuation of a predetermined controlled pulse duration of the laser236, the circuit trace 212 may begin to cure (and/or melt or soften) toan extent that a fusing bond may form between the material of thecircuit trace 212 and the electrical contact terminals (not shown) onthe die 220. This bond further assists in separating the unpackaged die220 from the wafer tape 218, as well as simultaneously affixing the die220 to the product substrate 210. Additionally, the laser 236 may causesome heat transfer on the wafer tape 218, thereby reducing adhesion ofthe die 220 to the wafer tape 218 and thus assisting in the transferoperation.

In other instances, dies may be released and fixed to the productsubstrates in many ways, including using a laser having a predeterminedwavelength or a focused light (e.g., IR, UV, broadband/multispectral)for heating/activating circuit traces to thereby cure an epoxy or phasechange bond materials, or for deactivating/releasing a die from wafertape, or for initiating some combination of reactions. Additionally, oralternatively, a specific wavelength laser or light may be used to passthrough one layer of the system and interact with another layer.Furthermore, a vacuum may be implemented to pull a die from the wafertape, and air pressure may be implemented to push the die onto a productsubstrate, potentially including a rotary head between the die wafersubstrate and the product substrate. In yet another instance, ultrasonicvibration may be combined with pressure to cause the die to bond to thecircuit traces.

Similar to the needle retraction support 230, the fixing mechanism mayalso include a product substrate support 238, which may be disposedbetween the laser 236 and the bottom surface of the product substrate210. The support 238 may include an opening 240 at a base end thereofand an opening 242 at an upper end thereof. For example, the support 238may be formed as a ring or hollow cylinder. The support may furtherinclude structure to secure a lens (not shown) to assist in directingthe laser. The laser 236 emits the light through the openings 240, 242to reach the product substrate 210. Furthermore, the upper end of thesidewalls of the support 238 may be disposed in direct contact with orclosely adjacent to the bottom surface of the product substrate 210.Positioned as such, the support 238 may help to prevent damage fromoccurring to the product substrate 210 during the stroke of the needle226 at the time of a transfer operation. In some instances, during thetransfer operation, the portion of the bottom surface of the productsubstrate 210 that is aligned with the support 238 may contact thesupport 238, which thereby provides resistance against the incomingmotion of the die 220 being pressed by the needle 226. Moreover, thesupport 238 may be movable in a direction of the vertical axis to beable to adjust a height thereof so as to raise and lower support 238 asnecessary, including to a height of the product substrate 210.

In addition to the above features, apparatus 200 may further include afirst sensor 244, from which apparatus 200 receives informationregarding the dies 220 on the wafer tape 218. In order to determinewhich die is to be used in the transfer operation, the wafer tape 218may have a bar code (not shown) or other identifier, which is read orotherwise detected. The identifier may provide die map data to theapparatus 200 via the first sensor 244.

As shown in FIGS. 2A and 2B, the first sensor 244 may be positioned nearthe transfer mechanism 206 (or the needle 226 specifically), spacedapart from the transfer mechanism 206 by a distance d, which may rangefrom about 1-5 inches, so as to enhance the accuracy of locationdetection. In an alternative embodiment, first sensor 244 may bedisposed adjacent the tip of the needle 226 in order to sense the exactposition of the dies 220 in real time. During the transfer process, thewafer tape 218 may be punctured and or further stretched over time,which may alter the previously mapped, and thus expected, locations ofthe dies 220 on the wafer tape 218. As such, small changes in thestretching of the wafer tape 218 could add up to significant errors inalignment of the dies 220 being transferred. Thus, real time sensing maybe implemented to assist in accurate die location.

In some instances, the first sensor 244 may be able to identify theprecise location and type of die 220 that is being sensed. Thisinformation may be used to provide instructions to the wafer tapeconveyor frame 222 indicating the exact location to which the wafer tape218 should be conveyed in order to perform the transfer operation.Sensor 244 may be one of many types of sensors, or a combination ofsensor types to better perform multiple functions. Sensor 244 mayinclude, but is not limited to: a laser range finder, or an opticalsensor, such as a non-limiting example of a high-definition opticalcamera having micro photography capabilities.

Moreover, in some instances, a second sensor 246 may also be included inapparatus 200. The second sensor 246 may be disposed with respect to theproduct substrate 210 so as to detect the precise position of thecircuit trace 212 on the product substrate 210. This information maythen be used to determine any positional adjustment needed to align theproduct substrate 210 between the transfer mechanism 206 and the fixingmechanism 208 so that the next transfer operation occurs in the correctlocation on the circuit trace 212. This information may further berelayed to the apparatus 200 to coordinate conveying the productsubstrate 210 to a correct position, while simultaneously conveyinginstructions to the wafer tape conveyor frame 222. A variety of sensorsare also contemplated for sensor 246 including optical sensors, such asone non-limiting example of a high-definition optical camera havingmicro photography capabilities.

FIGS. 2A and 2B further illustrate that the first sensor 244, the secondsensor 246, and the laser 236 may be grounded. In some instances, thefirst sensor 244, the second sensor 246, and the laser 236 may all begrounded to the same ground (G), or alternatively, to a different ground(G).

Depending on the type of sensor used for the first and second sensors244, 246, the first or second sensors may further be able to test thefunctionality of transferred dies. Alternatively, an additional testersensor (not shown) may be incorporated into the structure of apparatus200 to test individual dies before removing the product substrate 210from the apparatus 200.

Furthermore, in some examples, multiple independently-actuatable needlesand/or lasers may be implemented in a machine in order to transfer andfix multiple dies at a given time. The multiple needles and/or lasersmay be independently movable within a three-dimensional space. Multipledie transfers may be done synchronously (multiple needles going down atthe same time), or concurrently but not necessarily synchronously (e.g.,one needle going down while the other is going up, which arrangement maybalance better the components and minimize vibration). Control of themultiple needles and/or lasers may be coordinated to avoid collisionsbetween the plurality of components. Moreover, in other examples, themultiple needles and/or lasers may be arranged in fixed positionsrelative to each other.

Example Needle Tip Profile

As mentioned above, a profile shape of the tip 300 of a needle isdiscussed with respect to FIG. 3, which shows a schematic exampleprofile shape of the tip 300. In an embodiment, the tip 300 may bedefined as the end of the needle, including sidewalls 302 adjoiningtapered portion 304, corner 306, and base end 308, which may extendtransversely to the opposing side of the needle. The specific size andshape of the tip 300 may vary according to factors of the transferprocess such as, for example, the size of the die 220 being transferredand the speed and the impact force, of a transfer operation. Forexample, the angle θ seen in FIG. 3, as measured between a longitudinaldirection of the central axis of the needle and the tapered portion 304may range from about 10 to 15°; the radius r of the corner 306 may rangefrom about 15 to 50+ microns; the width w of the base end 308 may rangefrom about 0 to 100+ microns (μm), where w may be less than or equal tothe width of the die 220 being transferred; the height h of the taperedportion 304 may range from about 1 to 2 mm, where h may be greater thana distance traveled by needle during a stroke of a transfer operation;and the diameter d of the needle 226 may be approximately 1 mm.

Other needle tip profiles are contemplated and may have differentadvantages depending on various factors associated with the transferoperation. For example, the needle tip 300 may be more blunt to mirrorthe width of the die or more pointed so as to press in a smaller area ofthe wafer tape.

Example Needle Actuation Performance Profile

Illustrated in FIG. 4 is an embodiment of a needle actuation performanceprofile. That is, FIG. 4 depicts an example of the stroke patternperformed during a transfer operation by displaying the height of theneedle tip with respect to the plane of the wafer tape 218 as it varieswith time. As such, the “0” position in FIG. 4 may be the upper surfaceof the wafer tape 218. Further, inasmuch as the idle time of the needleand the ready time of the needle may vary depending on the programmedprocess or the varying duration of time between transferring a first dieand the time it takes to reach a second die for transfer, the dashedlines shown at the idle and ready phases of the stroke pattern indicatethat the time is approximate, but may be longer or shorter in duration.Moreover, it is to be understood that the solid lines shown for use ofthe laser are example times for an embodiment illustrated herewith,however, the actual duration of laser on and off time may vary dependingon the materials used in forming the circuit (such as the materialchoice of the circuit trace), the type of product substrate, the desiredeffect (pre-melting circuit trace, partial bond, complete bond, etc.),the distance of the laser from the bond point (i.e., the upper surfaceof the product substrate), the size of the die being transferred, andthe power/intensity/wavelength of the laser, etc. Accordingly, thefollowing description of the profile shown in FIG. 4 may be an exampleembodiment of a needle profile.

In some instances, prior to a transfer operation, a fully retractedneedle tip may be idle at approximately 2000 μm above the surface of thewafer tape. After a varying amount of time, the needle tip may descendrapidly to rest in the ready state at approximately 750 μm above thesurface of the wafer tape. After another undetermined amount of time atthe ready state, the needle tip may descend again to contact the die andpress the wafer tape with the die down to a height of approximately−1000 μm, where at the die may be transferred to the product substrate.The dotted vertical line at the start of the laser on section indicatesthat the laser may come on at some point between the beginning of thedescent from the ready phase and the bottom of the stroke of the needletip. For example, the laser may turn on at approximately 50% of the waythrough the descent. In some instances, by turning the laser on early,for example before the needle begins to descend, the circuit trace maybegin to soften prior to contact with the die so as to form a strongerbond, or additionally, the die wafer may be affected or prepared duringthis time. The phase in which the laser turns on may last approximately20 ms (“milliseconds”). At the bottom of the stroke, where the laser ison, that phase may be a bonding phase between the die and the productsubstrate. This bonding phase may allow the circuit trace to attach tothe die contacts, which stiffens quickly after the laser is turned off.As such, the die may be bonded to the product substrate. The bondingphase may last approximately 30 ms. Thereafter, the laser may be turnedoff and the needle may ascend to the ready phase rapidly. Conversely,the laser may be turned off before the needle begins to ascend, or atsome point during the ascent of the needle tip back to the ready phase,the laser may be turned off. After the ascent of the needle tip to theready phase, the height of the needle tip may overshoot and bounce backunder the height of the ready phase somewhat buoyantly. While some ofthe buoyancy may be attributed to the speed at which the needle tipascends to the ready phase, the speed and the buoyancy may beintentional in order to assist in retracting a tip of the needle from asurface of the wafer tape in the case where the needle has pierced thewafer tape and may be stuck therein.

As depicted in FIG. 4, the timing in which the laser is turned off maybe longer than the timing in which the laser is turned on, where aslower speed of the descent may assist in preventing damage to the die,and as mentioned above, the rapid rate of ascent may assist inextracting the needle tip from the wafer tape more effectively.Nevertheless, as previously stated, the timing shown on FIG. 4 isapproximate, particularly with respect to the idle and ready periods.Therefore, the numerical values assigned along the bottom edge of theFIG. 4 are for reference and should not be taken literally, except whenotherwise stated.

Example Product Substrate

FIG. 5 illustrates an example embodiment of a processed productsubstrate 500. A product substrate 502 may include a first portion of acircuit trace 504A, which may perform as a negative or positive powerterminal when power is applied thereto. A second portion of the circuittrace 504B may extend adjacent to the first portion of the circuit trace504A, and may act as a corresponding positive or negative power terminalwhen power is applied thereto.

As similarly described above with respect to the wafer tape, in order todetermine where to convey the product substrate 502 to perform thetransfer operation, the product substrate 502 may have a bar code (notshown) or other identifier, which is read or otherwise detected. Theidentifier may provide circuit trace data to the apparatus. The productsubstrate 502 may further include datum points 506. Datum points 506 maybe visual indicators for sensing by the product substrate sensor (forexample, second sensor 246 in FIG. 2) to locate the first and secondportions of the circuit trace 504A, 504B. Once the datum points 506 aresensed, a shape and relative position of the first and second portionsof the circuit trace 504A, 504B with respect to the datum points 506 maybe determined based on preprogrammed information. Using the sensedinformation in connection with the preprogrammed information, theproduct substrate conveyance mechanism may convey the product substrate502 to the proper alignment position for the transfer operation.

Additionally, dies 508 are depicted in FIG. 5 as straddling between thefirst and second portions of the circuit trace 504A, 504B. In thismanner, the electrical contact terminals (not shown) of the dies 508 maybe bonded to the product substrate 502 during a transfer operation.Accordingly, power may be applied to run between the first and secondportions of the circuit trace 504A, 504B, and thereby powering dies 508.For example, the dies may be unpackaged LEDs that were directlytransferred from a wafer tape to the circuit trace on the productsubstrate 502. Thereafter, the product substrate 502 may be processedfor completion of the product substrate 502 and used in a circuit orother final product. Further, other components of a circuit may be addedby the same or other means of transfer to create a complete circuit, andmay include control logic to control LEDs as one or more groups in somestatic or programmable or adaptable fashion.

Simplified Example Direct Transfer System

A simplified example of an embodiment of a direct transfer system 600 isillustrated in FIG. 6. The transfer system 600 may include a personalcomputer (PC) 602 (or server, data input device, user interface, etc.),a data store 604, a wafer tape mechanism 606, a product substratemechanism 608, a transfer mechanism 610, and a fixing mechanism 612.Inasmuch as a more detailed description of the wafer tape mechanism 606,the product substrate mechanism 608, the transfer mechanism 610, and thefixing mechanism 612 has been given heretofore, specific details aboutthese mechanisms is not repeated here. However, a brief description ofhow the wafer tape mechanism 606, the product substrate mechanism 608,the transfer mechanism 610, and the fixing mechanism 612 relate tointeractions between the PC 602 and the data store 604 is describedhereafter.

In some instances, the PC 602 communicates with data store 604 toreceive information and data useful in the transfer process of directlytransferring dies from a wafer tape in wafer tape mechanism 606 usingthe transfer mechanism 610 on to a product substrate in the productsubstrate mechanism 608 whereat the dies may be fixed upon the productsubstrate via actuation of a laser or other energy-emitting devicelocated in the fixing mechanism 612. PC 602 may also serve as areceiver, compiler, organizer, and controller of data being relayed toand from each of the wafer tape mechanism 606, the product substratemechanism 608, the transfer mechanism 610, and the fixing mechanism 612.PC 602 may further receive directed information from a user of thetransfer system 600.

Note that, while FIG. 6 depicts directional movement capability arrowsadjacent to the wafer tape mechanism 606 and the product substratemechanism 608, those arrows merely indicate general directions formobility, however, it is contemplated that both the wafer tape mechanism606 and the product substrate mechanism 608 may also be able to move inother directions including rotation in plane, pitch, roll, and yaw, forexample.

Additional details of the interaction of the components of the transfersystem 600 are described with respect to FIG. 7 below.

Detailed Example Direct Transfer System

A schematic of the communication pathways between the respectiveelements of a transfer system 700 may be described as follows.

The direct transfer system may include a personal computer (PC) 702 (orserver, data input device, user interface, etc.), which may receivecommunication from, and provide communication to a data store 704. ThePC 702 may further communicate with a first cell manager 706(illustrated as “Cell Manager 1”) and a second cell manager 708(illustrated as “Cell Manager 2”). Therefore, the PC 702 may control andsynchronize the instructions between the first cell manager 706 and thesecond cell manager 708.

PC 702 may include processors and memory components with whichinstructions may be executed to perform various functions with respectto the first and second cell managers 706, 708, as well as data store704. In some instances, PC 702 may include a project manager 710 and aneedle profile definer 712.

Project manager 710 may receive input from the first and second cellmanagers 706, 708 and data store 704 to organize the direct transferprocess and maintain smooth functioning with respect to orientation andalignment of the product substrate with respect to the wafer tape andthe dies thereon.

Needle profile definer 712 may contain data regarding the needle strokeperformance profile, which may be used to instruct the transfermechanism regarding the desired needle stroke performance according tothe specific dies on the loaded wafer tape and the pattern of thecircuit trace on the product substrate. Additional details of the needleprofile definer 712 are discussed further herein below.

Turning back to data store 704, data store 704 may include memorycontaining data such as a die map 714, which may be specific to thewafer tape loaded in the wafer tape mechanism. As explained previously,a die map may describe the relative locations of each die on the wafertape and the quality thereof for the purpose of providing apre-organized description of the location of specific dies. Further,data store 704 may also include memory containing circuit CAD files 716.Circuit CAD files 716 may contain data regarding a specific circuittrace pattern on the loaded product substrate.

Project manager 710 may receive the die map 714 and circuit CAD files716 from the data store 704, and may relay the respective information tothe first and second cell managers 706, 708, respectively.

In an embodiment, the first cell manager 706 may use the die map 714from data store 704 via a die manager 718. More specifically, diemanager 718 may compare die map 714 with the information received by asensor manager 720, and based thereon, may provide instructions to amotion manager 722 regarding the location of a particular die. Sensormanager 720 may receive data regarding the actual location of dies onthe wafer tape from a die detector 724. Sensor manager 720 may alsoinstruct the die detector 724 to look for a particular die in aparticular location according to die map 714. The die detector 724 mayinclude a sensor such as the second sensor 244 in FIGS. 2A and 2B. Basedon the received data of the actual location (either a confirmation or anupdate regarding a shift in position) of the dies on the wafer tape, themotion manager 722 may instruct a first robot 726 (illustrated as “Robot1”) to convey the wafer tape to an alignment position with the needle ofthe transfer mechanism.

Upon reaching the instructed location, the first robot 726 maycommunicate the completion of its movement to a needle controlboardmanager 728. Additionally, the needle control board manager 728 maydirectly communicate with the PC 702 to coordinate the execution of thetransfer operation. At the time of the execution of the transferoperation, the PC 702 may instruct the needle control board manager 728to activate the needle actuator/needle 730, thereby causing the needleto perform a stroke in accordance with the loaded needle profile in theneedle profile definer 712. The needle controlboard manager 728 may alsoactivate the laser control/laser 732, thereby causing the laser to emita beam toward the product substrate as the needle presses down a die viathe wafer tape to execute the transfer operation. As indicated above,the activation of the laser control/laser 732 may occur prior to,simultaneously, during, or after activation, or even a completeactuation, of the needle stroke.

Accordingly, the first cell manager 706 may pass through a plurality ofstates including: determining where to tell the first robot 726 to go;telling the first robot 726 to go to the determined location; turning onthe needle; activating the fixing device; and resetting.

Prior to execution of the transfer operation, the project manager 710may relay the data of the circuit CAD files 716 to the second cellmanager 708. The second cell manager 708 may include a sensor manager734 and a motion manager 736. Using the circuit CAD files 716, thesensor manager 734 may instruct the substrate alignment sensor 738 tofind the datum points on the product substrate and thereby detect andorient the product substrate according to the location of the circuittrace thereon. The sensor manager 734 may receive confirmation orupdated location information of the circuit trace pattern on the productsubstrate. The sensor manager 734 may coordinate with the motion manager736 to provide instructions to a second robot 740 (illustrated as “Robot2”) to convey the product substrate to an alignment position (i.e., atransfer fixing position) for execution of the transfer operation. Thus,the circuit CAD files 716 may assist the project manager 710 in aligningthe product substrate with respect to the wafer tape such that the diesmay be accurately transferred to the circuit trace thereon.

Accordingly, the second cell manager 708 may pass through a plurality ofstates including: determining where to tell the second robot 740 to go;telling the second robot 740 to go to the determined location; andresetting.

It is understood that additional and alternative communication pathwaysbetween all or fewer than all of the various components of the directtransfer system 700 described above are possible.

Example Direct Transfer Method

A method 800 of executing a direct transfer process, in which one ormore dies is directly transferred from a wafer tape to a productsubstrate, is illustrated in FIG. 8. The steps of the method 800described herein may not be in any particular order and as such may beexecuted in any satisfactory order to achieve a desired product state.The method 800 may include a step of loading transfer process data intoa PC and/or a data store 802. The transfer process data may include datasuch as die map data, circuit CAD files data, and needle profile data.

A step of loading a wafer tape into a wafer tape conveyor mechanism 804may also be included in method 800. Loading the wafer tape into thewafer tape conveyor mechanism may include controlling the wafer tapeconveyor mechanism to move to a load position, which is also known as anextract position. The wafer tape may be secured in the wafer tapeconveyor mechanism in the load position. The wafer tape may be loaded sothat the dies of the semiconductor are facing downward toward theproduct substrate conveyor mechanism.

The method 800 may further include a step of preparing the productsubstrate to load into the product substrate conveyor mechanism 806.Preparing the product substrate may include a step of screen printing acircuit trace on the product substrate according to the pattern of theCAD files being loaded into the PC or data store. Additionally, datumpoints may be printed onto the circuit substrate in order to assist inthe transfer process. The product substrate conveyor mechanism may becontrolled to move to a load position, which is also known as anextraction position, whereat the product substrate may be loaded intothe product substrate conveyor mechanism. The product substrate may beloaded so that the circuit trace faces toward the dies on the wafer. Insome instances, for example, the product substrate may be delivered andplaced in the load position by a conveyor (not shown) or other automatedmechanism, such as in the style of an assembly line. Alternatively, theproduct substrate may be manually loaded by an operator.

Once the product substrate is properly loaded into the product substrateconveyor mechanism in the wafer tape is properly loaded into the wafertape conveyor mechanism, a program to control the direct transfer of thedies from the wafer tape to the circuit trace of the product substratemay be executed via the PC to commence the direct transfer operation808. The details of the direct transfer operation are described below.

Example Direct Transfer Operation Method

A method 900 of the direct transfer operation of causing dies to betransferred directly from the wafer tape (or other substrate holdingdies, also called a “die substrate” for simplified description of FIG.9) to the product substrate is illustrated in FIG. 9. The steps of themethod 900 described herein may not be in any particular order and assuch may be executed in any satisfactory order to achieve a desiredproduct state.

In order to determine which dies to place on the product substrate andwhere to place the dies on the product substrate, the PC may receiveinput regarding the identification of the product substrate and theidentification of the die substrate containing the dies to betransferred 902. This input may be entered manually by a user, or the PCmay send a request to the cell managers in control, respectively, of theproduct substrate alignment sensor and the die detector. The request mayinstruct the sensor to scan the loaded substrate for an identificationmarker, such as a barcode or QR code; and/or the request may instructthe detector to scan the loaded die substrate for an identificationmarker, such as a barcode or QR code.

Using the product substrate identification input, the PC may query thedata store or other memory to match the respective identificationmarkers of the product substrate and the die substrate and retrieve theassociated data files 904. In particular, the PC may retrieve a circuitCAD file associated with the product substrate that describes thepattern of the circuit trace on the product substrate. The circuit CADfile may further contain data such as the number of, relative positionsof, and respective quality requirement of, the dies to be transferred tothe circuit trace. Likewise, the PC may retrieve a die map data fileassociated with the die substrate that provides a map of the relativelocations of the specific dies on the die substrate.

In the process of executing a transfer of a die to the productsubstrate, the PC may determine the initial orientation of the productsubstrate and the die substrate relative to the transfer mechanism andthe fixing mechanism 906. Within step 906, the PC may instruct thesubstrate alignment sensor to locate datum points on the productsubstrate. As discussed above, the datum points may be used as referencemarkers for determining the relative location and orientation of thecircuit trace on the product substrate. Further, the PC may instruct thedie detector to locate one or more reference points on the die substrateto determine the outlay of the dies.

Once the initial orientation of the product substrate and die substrateare determined, the PC may instruct the respective product substrate anddie substrate conveyance mechanisms to orient the product substrate anddie substrate, respectively, into a position of alignment with thetransfer mechanism and the fixing mechanism 908.

The alignment step 908 may include determining the location of theportion of the circuit trace to which a die is to be transferred 910,and where the portion is located relative to the transfer fixingposition 912. The transfer fixing position may be considered to be thepoint of alignment between the transfer mechanism and the fixingmechanism. Based on the data determined in steps 910 and 912, the PC mayinstruct the product substrate conveyance mechanism to convey theproduct substrate so as to align the portion of the circuit trace towhich a die is to be transferred with the transfer fixing position 914.

The alignment step 908 may further include determining which die on thedie substrate will be transferred 916, and where the die is locatedrelative to the transfer fixing position 918. Based on the datadetermined in steps 916 and 918, the PC may instruct the wafer tapeconveyance mechanism to convey the die substrate so as to align the dieto be transferred with the transfer fixing position 920.

Once the die to be transferred from the die substrate and the portion ofthe circuit trace to which a die is to be transferred are aligned withthe transfer mechanism and the fixing mechanism, the needle and thefixing device (e.g., laser) may be actuated 922 to effectuate thetransfer of the die from the die substrate to the product substrate.

After a die is transferred, the PC may determine whether additional diesare to be transferred 924. In the case where another die is to betransferred, the PC may revert to step 908 and realign the product anddie substrates accordingly for a subsequent transfer operation. In thecase where there will not be another die transferred, the transferprocess is ended 926.

Example Direct Transfer Conveyor/Assembly Line System

In an embodiment described with respect to FIG. 10, several of thecomponents of the direct transfer apparatus described above may beimplemented in a conveyor/assembly line system 1000 (hereinafter“conveyor system”). In particular, FIGS. 2A and 2B depict the productsubstrate 210 being held by the product substrate conveyor frame 214 andtensioned by the product substrate tensioner frame 216. As analternative to securing a product substrate conveyor frame 214 in aconfined area via a system of motors, rails, and gear as indicated withrespect to apparatus 200, FIG. 10 illustrates the product substrateconveyor frame 214 being conveyed through the conveyor system 1000 inwhich the product substrate goes through an assembly line style process.As the actual means of conveyance between operations being performed onthe product substrate being conveyed, the conveyor system 1000 mayinclude a series of tracks, rollers, and belts 1002 and/or otherhandling devices to sequentially convey a plurality of product substrateconveyor frames 214, each holding a product substrate.

In some instances, operation stations of the conveyor system 1000 mayinclude one or more printing stations 1004. As blank product substratesare conveyed to the printing station(s) 1004, a circuit trace may beprinted thereon. In the case that there are multiple printing stations1004, the multiple printing stations 1004 may be arranged serially, andmay be configured to perform one or more printing operations each so asto form a complete circuit trace.

Additionally, in the conveyor system 1000, the product substrateconveyor frame 214 may be conveyed to one or more die transfer stations1006. In the event that there are multiple die transfer stations 1006,the multiple die transfer stations 1006 may be arranged serially, andmay be configured to perform one or more die transfers each. At thetransfer station(s), the product substrates may have one or more diestransferred and affixed thereto via a transfer operation using one ormore of the direct transfer apparatus embodiments described herein. Forexample, each transfer station 1006 may include a wafer tape conveyancemechanism, a transfer mechanism, and a fixing mechanism. In someinstances, a circuit trace may have been previously prepared on theproduct substrate, and as such, the product substrate may be conveyeddirectly to the one or more transfer stations 1006.

In the transfer stations 1006, the wafer tape conveyance mechanism, thetransfer mechanism, and the fixing mechanism may be aligned with respectto the conveyed product substrate conveyor frame 214 upon entering thestation. In this situation, the transfer station 1006 components mayrepeatedly perform the same transfer operation in the same relativeposition on each product substrate as the plurality of productsubstrates are conveyed through the conveyor system 1000.

Moreover, the conveyor system 1000 may further include one or morefinishing stations 1008 to which the product substrate may be conveyedto have final processing performed. The type, amount, and duration ofthe final processing may depend on the features of the product and theproperties of the materials used to make the product. For example, theproduct substrate may receive additional curing time, a protectivecoating, additional components, etc., at the finishing station(s) 1008.

Second Example Embodiment of a Direct Transfer Apparatus

In another embodiment of a direct transfer apparatus, as seen in FIGS.11A and 11B, a “light string” may be formed. While many of the featuresof apparatus 1100 may remain substantially similar to those of apparatus200 of FIGS. 2A and 2B, product substrate conveyance mechanism 1102, asdepicted in FIGS. 11A and 11B, may be configured to convey a productsubstrate 1104 that is different than the product substrate 212.Specifically, in FIGS. 2A and 2B, the product substrate conveyancemechanism 202 includes the conveyor frame 214 and the tensioner frame216, which secure the sheet-like product substrate 212 under tension. Inthe embodiment of FIGS. 11A and 11B, however, the product substrateconveyance mechanism 1102 may include a product substrate reel system.

The product substrate reel system may include one or two circuit tracereels 1106 that are wound with a “string circuit,” which may include apair of adjacently wound conductive strings or wires as the productsubstrate 1104. In an instance with only one reel, the reel 1106 may belocated on a first side of the transfer position, and the pair ofconductive strings (1104) may be wound around the single reel 1106.Alternatively, there may be two circuit trace reels 1106 located on thefirst side of the transfer position, where each reel 1106 contains asingle strand of the string circuit and the strands are then broughttogether to pass through the transfer position.

Regardless of whether one reel 1106 or two reels 1106 are implemented,the die transfer process of forming the string circuit may besubstantially similar in each case. In particular, the conductivestrings of the product substrate 1104 may be threaded from the reel(s)1106 across the transfer position and may be fed into a finishing device1108. In some instances, the finishing device 1108 may be: a coatingdevice to receive a protective coating, for example, of a translucent ortransparent plastic; or a curing apparatus, which may finish curing thestring circuit as a part of final processing of the product.Additionally, or alternatively, the circuit string may be fed ontoanother reel, which may wind up the string circuit thereon before finalprocessing of the string circuit. As the conductive strings of theproduct substrate 1104 are pulled through the transfer position, thetransfer mechanism 206 may be actuated to perform a needle stroke (asdescribed above) to transfer dies 220 to the conductive strings of theproduct substrate 1104 so that electrical contact terminals of the dies220 are placed, respectively, on the adjacent strings, and the fixingmechanism 208 may be actuated to affix the dies 220 in position.

Furthermore, apparatus 1100 may include tensioning rollers 1110 on whichthe conductive strings of the product substrate 1104 may be supportedand further tensioned against. Thus, the tensioning rollers 1110 mayassist in maintaining tension in the formed string circuit so as toenhance the die transfer accuracy.

In FIG. 11B, dies 220 are depicted as having been transferred to theconductive strings of the product substrate 1104, thereby uniting (tosome extent) the conductive strings of the product substrate 1104 andforming a string circuit.

Third Example Embodiment of a Direct Transfer Apparatus

In an additional embodiment of a direct transfer apparatus, as seen inFIG. 12, apparatus 1200 may include a wafer tape conveyance mechanism1202. In particular, in lieu of the wafer tape conveyor frame 222 andthe tensioner frame 224 shown in FIGS. 2A and 2B, the wafer tapeconveyance mechanism 1202 may include a system of one or more reels 1204to convey dies 220 through the transfer position of the apparatus 1200to transfer dies to a single substrate. In particular, each reel 1204may include a substrate 1206 formed as a narrow, continuous, elongatedstrip having dies 220 attached consecutively along the length of thestrip.

In the case where a single reel 1204 is used, a transfer operation mayinclude conveying the product substrate 210 via the product substrateconveyance mechanism 202 substantially as described above, using motors,tracks, and gears. However, the wafer tape conveyance mechanism 1202 mayinclude a substantially static mechanism, in that, while the dies 220may be fed continuously through the transfer position by unrolling thesubstrate 1206 from reel 1204, the reel 1204 itself main remain in afixed position. In some instances, the tension of the substrate 1206 maybe maintained for stability purposes by tensioning rollers 1208, and/ora tensioning reel 1210, which may be disposed on a side of the apparatus1200 opposite the reel 1204. The tensioning reel 1210 may roll up thesubstrate 1206 after the dies have been transferred. Alternatively, thetension may be maintained by any other suitable means to secure thesubstrate 1206 so as to assist in pulling it through the transferposition after each transfer operation to cycle through the dies 220.

In an embodiment where multiple reels 1204 are used, each reel 1204 maybe disposed laterally adjacent to other reels 1204. Each reel 1204 maybe paired with a specific transfer mechanism 206 and a specific fixingmechanism 208. In this case, each respective set of transfer mechanismsand fixing mechanisms may be arranged with respect to the productsubstrate 210 such that multiple dies may be placed in multiplelocations on the same product substrate 210 simultaneously. For example,in some instances, the respective transfer positions (i.e., thealignment between a transfer mechanism and a corresponding fixingmechanism) may be in a line, offset, or staggered so as to accommodatevarious circuit trace patterns.

Regardless of whether one reel 1204 or a plurality of reels 1204 areimplemented, the die transfer operation may be relatively similar to thetransfer operation as described above with respect to the first exampleembodiment of the direct transfer apparatus 200. For instance, theproduct substrate 210 may be conveyed to a transfer position (die fixingposition) in the same manner as described above via the productsubstrate conveyance mechanism 202, the transfer mechanism(s) 206 mayperform a needle stroke to transfer the die 220 from the die substrate1206 to the product substrate 210, and the fixing mechanism 208 may beactuated to assist in affixing the die 220 to the product substrate 210.

Note that in an embodiment with a plurality of reels 1204, a circuittrace pattern may be such that not every transfer mechanism may need tobe actuated simultaneously. Accordingly, multiple transfer mechanismsmay be actuated intermittently as the product substrate is conveyed tovarious positions for transfer.

Fourth Example Embodiment of a Direct Transfer Apparatus

FIG. 13 depicts an embodiment of a direct transfer apparatus 1300. As inFIGS. 2A and 2B, the product substrate conveyance mechanism 202 may bedisposed adjacent to the wafer tape conveyance mechanism 204. However,there is a space between the conveyance mechanisms 202, 204 in which atransfer mechanism 1302 may be disposed to effectuate the transfer ofthe dies 220 from the wafer tape 218 to the product substrate 210.

The transfer mechanism 1302 may include a collet 1304 that picks thedies 220, one or more at a time, from the wafer tape 218 and rotatesabout an axis A that extends through arm 1306. For example, FIG. 13depicts the wafer tape 218 facing the product substrate 210 such thatthe collet 1304 may pivot 180 degrees about pivot point 1308 (seedirectional pivot arrows) between the die-carrying surface of the wafertape 218 and the transfer surface of the product substrate 210. That is,the direction of extension of the collet 1304 pivots in a plane that isorthogonal to the surface or plane of transfer of both the wafer tape218 and the product substrate 210. Alternatively, in some embodiments,the arm structure of the collet may be arranged to pivot between twoparallel surfaces, and the arm of the collet may pivot along parallelplane. Thus, when facing the wafer tape 218, the collet 1304 may pickthe die 220 and then immediately pivot to the surface of the productsubstrate 210 to be in line with the fixing mechanism 208. The collet1304 then releases the die 220 so as to transfer the die 220 to beaffixed to the circuit trace 212 on the product substrate 210.

In some instances, the transfer mechanism 1302 may include two or morecollets (not shown) extending from the arm in different directions. Insuch an embodiment, the collets may be indexed rotatingly 360 degreesthrough the collet stop locations and picking and transferring a dieevery time a collet passes the wafer tape 218.

Additionally, the one or more collets 1304 may pick and release the dies220 from the wafer tape using positive and negative vacuum pressurethrough the collet 1304.

CONCLUSION

Although several embodiments have been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the claims are not necessarily limited to the specific features oracts described. Rather, the specific features and acts are disclosed asillustrative forms of implementing the claimed subject matter.Furthermore, the use of the term “may” herein is used to indicate thepossibility of certain features being used in one or more variousembodiments, but not necessarily in all embodiments.

What is claimed is:
 1. A system to transfer an unpackaged semiconductordevice die (“unpackaged die”) directly from a die holding substrate to atransfer location on a secondary substrate, the system comprising: aprocessor; memory storing transfer instructions, the memory being incommunication with the processor; a die separation device including atransfer member disposed adjacent to the die holding substrate toinitiate separation of the unpackaged die from the die holdingsubstrate; a first sensor to detect a position of the unpackaged die,the first sensor disposed adjacent to the die holding substrate andspaced apart from the transfer member a distance ranging from about 1inch to about 5 inches, and the first sensor to send first data to thememory, the first data representing the position of the unpackaged die;and a second sensor to detect a position and orientation of thesecondary substrate with respect to the unpackaged die on the dieholding substrate, and the second sensor to send second data to thememory, the second data representing the position and orientation of thesecondary substrate, wherein the processor is in communication with thedie separation device, the first sensor, and the second sensor, whereinthe memory stores the first data and the second data, and wherein theprocessor is configured to receive the transfer instructions withrespect to the first data and the second data from the memory to causeactuation of the die separation device according, at least in part, tothe transfer instructions, the first data, and the second data.
 2. Thesystem according to claim 1, wherein the transfer member is sized totransfer at least the unpackaged die via a pressing contact between thetransfer member and a side of the unpackaged die in a direction towardthe transfer location.
 3. The system according to claim 2, wherein thetransfer member includes a needle configured to reciprocate between anon-contact position and a contact position with the side of theunpackaged die, and wherein, in the contact position, the pressingcontact causes at least one peripheral edge of the unpackaged die toprotrude away from the die holding substrate.
 4. The system according toclaim 1, wherein the transfer member includes a collet that is pivotablebetween the die holding substrate and the secondary substrate, thecollet arranged to remove the unpackaged die from the die holdingsubstrate and pivot to place the unpackaged die on the secondarysubstrate.
 5. The system according to claim 4, wherein the collet pivotsin a plane that is orthogonal to both a plane of the die holdingsubstrate and a plane of the secondary substrate.
 6. The systemaccording to claim 1, wherein the second sensor includes at least oneof: a laser range finder or an optical sensor.
 7. The system accordingto claim 1, wherein the die separation device includes a plurality oftransfer members.
 8. The system according to claim 1, wherein the firstsensor includes at least one of: a laser range finder or an opticalsensor.